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Biomedical subjects

A Kojima

Publications and source records attributed to A Kojima.

At least 307 records · Page 17Linked to original sources
PubMed1979

Augmentation of delayed-type hypersensitivity and resistance against allogeneic or syngeneic methylcholanthrene-induced tumors in mice preimmunized with the tumor extracts.

Delayed-type hypersensitivity (DTH) responses against methylcholanthrene-induced fibrosarcomas in C3H/He and BDF1 mice were developed in BDF1 mice by sc injection of the respective mitomycin C-treated tumor cells. The DTH responses to the allogeneic and the syngeneic tumor cells were accelerated and enhanced tumor-specifically by priming 7 days previously with KCl extracts of the respective tumors. The ability in the mice primed with the tumor extracts enhancing the DTH response against the tumor cells could be transferred to recipient mice by the spleen cells, but not by the T-cell-depleted spleen cells. Rejection of allogeneic tumor was accelerated under the development of accelerated and enhanced DTH response against the allogeneic tumor antigens. Moreover, resistance to syngeneic tumor growth increased significantly with the development of accelerated and enhanced DTH response against the syngeneic tumor antigens. Thus, the augmentation of DTH response by preimmunization with tumor extracts was accompanied by the increased resistance to tumor growth, suggesting that T cells involved in the augmentation of tumor-specific DTH response play some role in increasing the resistance to tumor growth.

Animals↗
PubMed1979

Prevalent types of tumors developing in neonatally thymectomized mice.

Tumor development was observed for 24 months in neonatally thymectomized (nTx) and normal (C3H/HeMs x 129/J)F1 mice. Thymectomy was performed at 3 days of age. Ovarian (29%, with significant difference from the control at P less than 0.001), pituitary (6%, P less than 0.08), and lymphoreticular tumors (16%, P less than 0.05) were observed in higher incidence in nTx females compared with normal controls, resulting in a significant increase in overall tumor incidence (99 tumors in 114 nTx females vs. 37 tumors in 71 normal females, P less than 0.01). No apparent difference in overall tumor incidence was observed between nTx and non-Tx males. Also, there was no higher risk for lung, liver, and mammary tumors in males and females after neonatal thymectomy. The finding that increased tumor incidence was limited to endocrine and lymphoreticular tissues does not support the concept of immune surveillance of carcinogenesis, but rather suggests the importance of tumor-prone conditioning of endocrine or immune systems as a result of neonatal thymectomy.

Animals↗
PubMed1979

Regulatory role of suppressor T cells in the expression of delayed-type hypersensitivity in mice. I. Transient appearance of suppressor T cells for the expression of delayed footpad reaction induced with lipid-conjugated lysozyme.

Delayed footpad reaction (FPR) to lysozyme (Lys) in mice was induced without antibody responses by lipid-conjugated lysozyme (D.Lys). This FPR was suppressed by priming s.c. with a high dose (10 mg) of Lys 2 weeks previously (unresponsiveness). Spleen cells from the unresponsive mice suppressed antigen-specifically FPR in mice previously immunized with D.Lys, and also suppressed passive transfer of FPR by D.Lys-immune lymphoid cells into normal mice. The suppressive activity of the spleen cells was abolished by treatment with anti-phi anti-serum and complement. The suppressor cells occurred also in the thymus of unresponsive mice. Unresponsiveness was induced in mice immediately after priming with Lys and persisted at least up to 7 weeks after the induction. In contrast, suppressor cells appeared only 2 weeks after induction of unresponsiveness in both the spleen and the thymus but were no longer detectable 3-7 weeks later, although donor mice remained fully unresponsive. These results suggest that antigen-specific suppressor T cells are involved in the regulation of the expression of FPR only for a definite period of time in unresponsive mice.

Animals↗
PubMed1979

Regulatory role of suppressor T cells in the expression of delayed-type hypersensitivity in mice. II. Soluble factor from thymic suppressor cells stimulated with antigen in vitro and its possible interaction with macrophages.

Thymus cells from mice primed s.c. with a high dose (10 mg) of lysozyme (Lys) specifically suppressed delayed footpad reaction (FPR) in mice previously immuned with lipid-conjugated lysozyme (D.Lys), and also suppressed the transfer of FPR by D.Lys-immune spleen cells into normal mice. Furthermore, they inhibited antigen-stimulated DNA synthesis of D.Lys-immune spleen cells in vitro. If the suppressor thymus cells were cultured with Lys in vitro, they produced soluble factor which depressed the ability of D.Lys-immune spleen cells to transfer FPR. Both supernatant of culture without Lys and extract of suppressor thymus cells were inactive in supression of FPR. The suppressor factor was antigen-specific because its suppressive activity was absorbed with Lys but not with an unrelated antigen lactalbumin. The factor failed to depress the ability of D.Lys-immune spleen cells to transfer FPR when the spleen cells were depleted of glass-adherent cells. In addition, incubation of peritoneal exudate cells from normal mice with the factor rendered the cells suppressive for passive transfer of FPR. These results suggest that the suppressor factor depresses the effector function of T cells responsible for FPR possibly via macrophage.

Animals↗
PubMed1979

Preferential induction of memory T cells for delayed-type hypersensitivity with reduced and alkylated human serum albumin in mice.

Reduction and alkylation of human serum albumin (HSA) resulted in molecular aggregation of the protein. The reduced and alkylated antigen (RA-HSA) was lacking in the ability to induce delayed-type hypersensitivity (DTH) response as well as antibody response to native HSA in mice, although native HSA induced both responses. On the other hand, RA-HSA could stimulate a priming function that accelerated and enhanced the DTH response to native HSA, which, however, failed to stimulate the function. Thus, DTH-related memory activity was dissociated from DTH-related effector activity. The DTH-related memory activity, manifested by the accelerated an enhanced response in RA-HSA-primed mice, could be transferred antigen-specifically by their spleen cells and T-cell enriched fraction, but not by their T-cell depleted spleen cells. The RA-HSA-primed T cells, however, failed to transfer the effector function for DTH response. These results suggested that DTH-related memory T cells belong to different subset(s) of T cells from effector T cells for a DTH response.

Animals↗
PubMed1976

[The histaminergic mechanisms in the regulation of prolactin secretion in urethan-anesthetized rats (author's transl)].

In an attempt to detect the existence of histaminergic mechanisms in the regulation of prolactin secretion in rats, the effects of histidine and histamine-receptor antagonists (chlorpheniramine and metiamide) on plasma prolactin levels in urethan-anesthetized rats were investigated in relation to other aminergic mechanisms. Chlorpheniramine was used as an H1-receptor antagonist and metiamide as an H2-receptor antagonist. Wistar male rats were used under urethan anesthesia and blood was obtained by cardiac puncture. Rat plasma prolactin was measured by radioimmunoassay. As already reported, L-DOPA and diethyldithiocarbamate markedly decreased plasma prolactin levels in rats. Dihydroxyphenylserine increased prolactin levels. Brocresine phosphate, a histidine decarboxylase inhibitor, markedly stimulated prolactin secretion in urethan-anesthetized rats. This stimulation was not blocked by pretreatment with histidine or L-DOPA. Histidine alone did not affect plasma levels of prolactin or methyldopamine-induced increase in plasma prolactin levels. On the other hand, histidine significantly stimulated prolactin secretion in chlorpheniramine-treated rats. In contrast, histidine depressed plasma prolactin levels in metiamide-treated rats. These findings indicate that a dopaminergic component is inhibitory and a noradrenergic one is stimulatory in prolactin secretion in rats and further that there exist the histaminergic mechanisms, relatively independent from other aminergic mechanisms, which might also play an important role in the regulation of prolactin secretion in rats. Furthermore, it is suggested that H1-receptor is stimulatory and H2-receptor is inhibitory in prolactin secretion in rats.

Animals↗
PubMed1976

Venous pressure and compliance of the peripheral capacitance vessels.

Compliances of the peripheral capacitance vessels decreased gradually in accordance with the increase in pressure of the brachial vein. The relationship between them formed a number of hyperbolic-like curves, the same results as those found in many cases of both normal subjects and patients with congestive heart failure. The decrease of compliance of the peripheral capacitance vessels was not the result of an organic change, but of a functional change of the vessels caused by distention.

Adult↗
PubMed1976

Abnormal thyroid function in spontaneously hypertensive rats.

Thyroid weight, thyroidal radioiodide uptake, and cyclic AMP-dependent protein kinase activity of a thyroid supernatant fraction were increased significantly in spontaneously hypertensive rats (SHR), apparently because of increased secretion of pituitary TSH. However, the thyroids of SHR did not make supernormal amounts of thyroxine (T4), and thyroidal radioiodine release was apparently impaired. In the SHR, proteolytic enzyme activity was less than normal and the thyroglobulin was more resistant to normal proteolytic enzyme than was control thyroglobulin. Presumably because of these abnormalities, plasma T4 was significantly lower than normal, but triiodothyronine (T4) was normal, as a result of compensatory processes occurring in T3 synthesis and hydrolysis of thyroglobulin. T4 and T3 were less effective in depressing pituitary TSH synthesis and secretion in SHR than in controls, possibly because of an abnormal setting of the "hormostat." Although the hypothalamic content of TRH was normal in SHR, the exact site of the abnormality in the "hormostat" is not delineated in the present study.

Animals↗
PubMed1976

Effects of excess iodide and other anions on thyroid hormone secretion in normal or hypophysectomized rats treated with graded doses of thyroid hormone.

In order to obtain further information about the stimulatory action of excess iodide on thyroid hormone secretion in thyroxine (T4)-treated rats, experiments were performed in hypophysectomized rats, or rats treated with graded doses of T4 or triiodothyronine (T3).T3 as well as T4 played a permissive role in the production of the iodide effect in normal animals, but T3 was more effective than T4. Excess iodide stimulated thyroid hormone secretion in hypophysectomized animals, this finding being compatible with the hypothesis that, by inhibiting TSH secretion, T3 and T4 produced a condition in which excess iodide stimulated thyroid hormone secretion in intact rats. However, T4 played an additional role in thyroid hormone secretion by acting directly on the thyroid. In hypophysectomized animals, small doses of T4 stimulated thyroid hormone secretion, and this action was additive to that of excess iodide, whereas large doses of T4 were inhibitory and reduced the effectiveness of excess iodide. The stimulatory action on thyroid hormone secretion was specific for iodide and was not shared by other anions. The action of excess iodide was blocked by methimazole. We suggest that excess iodide stimulates thyroid hormone secretion by increasing intrathyroidal concentrations of cyclic AMP in the absence of TSH, and that this increase in cyclic AMP concentration is blocked by methimazole.

Animals↗